title: Heat-tolerant versus heat-sensitive Bos taurus cattle: influence of air temperature and breed on the metabolic response to a provocative immune challenge.
abstract: The response of the immune and stress systems have been assessed in response to a lipopolysaccharide (LPS) challenge, yet the role of metabolism in mediating energy requirements during the acute phase response has not been sufficiently studied. This study tested heat-tolerant (Romosinuano [RO]) and heat-sensitive (Angus [ANG]) Bos taurus breeds at different ambient temperatures (Ta) to determine differential metabolic responses to LPS challenge. Twenty-one heifers (ANG: n = 11, 306 ± 26 kg BW; RO: n = 10, 313 ± 32 kg BW) were housed in stanchions in 4 temperature-controlled chambers. Initially, Ta in all 4 chambers was cycling at thermoneutrality (TN; 18.5°C-23.5°C) for a 1-wk adjustment period, followed by an increase in 2 chambers to cycling heat stress (HS; 24°C-38°C) for 2 wk. Five ANG and 5 RO heifers were housed at TN, whereas 6 ANG and 5 RO heifers were housed at HS. On day 19, heifers were fitted with jugular catheters. On day 20, heifers were challenged with LPS (0.5 μg/kg BW; 0 h), and blood samples were collected from -2 to 8 h and at 24 h relative to LPS challenge. Serum was analyzed for glucose, insulin, and NEFA concentrations. In addition, feed intake was measured 3 d before and on the day of the challenge. Feed intake decreased over time (P < 0.001) and was decreased in heifers housed at HS compared with heifers housed at TN (P = 0.013). Glucose concentrations before LPS challenge were greater in RO (P = 0.01) than in ANG heifers and greater in TN-housed heifers (P = 0.02) than in HS heifers. Glucose after LPS challenge initially increased before decreasing below baseline concentrations (P < 0.01) in all heifers. In addition, there was a breed by Ta interaction (P < 0.004), such that HS decreased glucose concentrations in ANG heifers compared with ANG heifers housed at TN (P < 0.001), whereas HS did not affect glucose concentrations after LPS challenge in RO heifers (P = 0.941). Nonesterified fatty acid concentrations before LPS challenge were not affected by breed (P = 0.37) or Ta (P = 0.60). Although NEFA concentration after LPS challenge was unaffected by Ta (P = 0.78), there tended to be a breed by Ta interaction (P = 0.07) such that, when housed at HS, RO heifers had greater serum NEFA concentrations after LPS challenge than ANG heifers (P = 0.009). Insulin concentration before LPS challenge was greater in RO heifers than in ANG heifers (P < 0.01). Insulin after LPS challenge increased (P < 0.01), with RO heifers producing a greater insulin response than ANG heifers (P < 0.01). These data suggest that HS decreases the metabolic response of heat-sensitive ANG heifers in response to LPS challenge, thus providing physiological evidence that may explain differences observed in the acute phase response between heat-sensitive ANG and heat-tolerant RO cattle breeds.
authors.affiliation: USDA Agricultural Research Service, Livestock Issues Research Unit, Lubbock, TX 79403, USA.
authors.forename: N C
authors.initials: NC
authors.lastname: Burdick Sanchez
authors.forename: R
authors.initials: R
authors.lastname: Chaffin
authors.forename: J A
authors.initials: JA
authors.lastname: Carroll
authors.forename: C C
authors.initials: CC
authors.lastname: Chase
authors.forename: S W
authors.initials: SW
authors.lastname: Coleman
authors.forename: D E
authors.initials: DE
authors.lastname: Spiers
mesh_terms: D000210:Acute-Phase Reaction / Q000235:genetics / Q000662:veterinary; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001947:Breeding; D002417:Cattle / Q000235:genetics / Q000502:physiology*; D002418:Cattle Diseases / Q000235:genetics; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D006358:Hot Temperature / Q000009:adverse effects*; D007109:Immunity / Q000502:physiology*; D007328:Insulin / Q000097:blood; D008070:Lipopolysaccharides / Q000276:immunology; D013045:Species Specificity; D013312:Stress, Physiological / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D013696:Temperature
chemical_list: D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D008070:Lipopolysaccharides
keywords: Angus; Heat stress; Lipopolysaccharide; Metabolism; Romosinuano